Hammermills are often used to reduce the size of solid material. Materials often used in hammermills include coal, asphalt, cement, limestone, chemical fertilizer, barks, rocks, minerals, and food products. The materials are often fed into an inlet where the material falls into a milling chamber. The milling chamber typically comprises a plurality of impact hammers and may comprise a screen. The impact hammers are typically fastened at a proximal end to a rotary assembly; they are either rigidly fixed to the rotor assembly or the impact hammers may be free-swinging. As the material is fed into the chamber, the rotary assembly rotates bringing the impact hammers into contact with the material. The size reduction on each impact depends on the differential speed between the hammers and material, size of the material, and hardness of the material. If a screen is present, the screen may allow only the desired material particle size to pass to the outside of the chamber to an outlet where the particles can be collected or funneled to another machine where the material may be further processed.
Due to the impact and/or abrasive nature of the material, the impact hammers may wear requiring continual maintenance and down time of the hammermill.
U.S. Pat. No. 6,405,950 by Gunderson which is herein incorporated by reference for all that it contains, discloses an improved airflow hammermill assembly for grinding materials. The improved airflow hammermill assembly incorporates one or more diverging ducts communicating with the hammermill housing to provide a more uniform negative pressure within the housing. The improved airflow hammermill assembly allows increased throughput and energy savings.
U.S. Pat. No. 5,938,131 by Thom, Jr., et al., which is herein incorporated by reference for all that it contains, discloses a hammermill that includes a housing, a working chamber defined by a polygonal screen, an inlet to the chamber, an outlet and a plurality of free-swinging hammers attached to a driven rotor. Support brackets extend the length of the housing and mount deflectors for eliminating tangential motion of materials being comminuted in the working chamber in the region of the deflectors.
U.S. Pat. No. 4,638,747 by Brock, et al., which is herein incorporated by reference for all that it contains, discloses an invention that comprises a coal-fired burner system for use in a drum mix asphalt plant or drum dryer used for producing asphalt paving composition.
U.S. Patent Publication 2004/0129808 by Crane, et al., which is herein incorporated by reference for all that it contains, discloses a hammermill for singulating cellulosic fibers from a pulp sheet that comprises a cylindrical housing, a feed slot with a breaker bar positioned therein and a rotor mounted for rotation in the housing. Feed rolls are provided to feed a sheet of pulp into the feed slot upstream of the breaker bar.